1. Field of the Invention
The present invention relates to a method of manufacturing a liquid storage container, and relates in particular to an arrangement for injecting a liquid into a liquid storage container provided with a liquid absorption member for retaining the liquid such as ink.
2. Description of the Related Art
As this kind of a liquid storage container, an ink tank that is employed for inkjet printing is well known, and one form of ink tank internally includes an ink absorption member for absorbing ink. FIG. 6 is an exploded perspective view showing an example of such a conventional ink tank made by integrating a print head portion and an ink tank portion in which ink to be supplied to the print head is stored.
As shown in FIG. 6, an ink tank H100 includes an ink absorption member H300 that is inserted into the ink tank in a compressed state, and an ink H400 permeates the ink absorption member H300 and is retained by the ink absorption member H300. Here, a balance is adjusted between an ink retention force of the ink absorption member H300 and a meniscus retention force at the ink ejection opening of the print head to be in a certain range, so that a satisfactory ink supply condition can be obtained without a leakage occurring at the ink ejection opening. In this arrangement, a filter H200 is provided between the ink absorption member H300 and the print head portion. A hole and a groove are formed in a cover member H500 of the ink tank, and a sealing member H600, for covering the hole and the groove, is attached to the cover member H500. This allows an air communication port H510 for adjusting fluctuations in the internal pressure of the ink tank H100 to be formed.
In a distribution of ink tanks, there is possibilities that contents of a ink tank freeze when the ink tanks are in cold areas or when the ink tanks are stored in a warehouse wherein air conditioning is not provided. If the freezing of the ink tank occurs, the leakage of ink may occur. FIGS. 7A to 7D are views illustrating this leakage phenomenon. For the ink tank shown in FIG. 6, there may be a case, as shown in FIG. 7A, where ink has unevenly permeated the ink absorption member H300, and an interface I formed with ink is made concavo-convex. In this case, when, for example, ink H400 freezes in a position of the ink tank in which the air communication port H510 faces downward, freezing expands the volume of the ink H400 permeating the ink absorption member H300. As a result, the ink H400 moves into a layer H310, which is the portion of the ink absorption member H300 that the ink H400 has not permeated. Consequently, the volume of the ink un-permeated layer H310 of the ink absorption member H300 is reduced, as shown in FIG. 7B.
If the distribution of the ink permeating the ink absorption member H300 is not uniform and thus the ink un-permeated layer H310 has a comparatively thin portion as shown in FIG. 7C, the thin portion of the ink un-permeated layer H310 disappears by repeating freezing and melting of the ink only a number of times. As a result, further freezing and melting cause the ink to be moved and to ooze from a portion where the ink un-permeated layer H310 has disappeared, and thus ink may leak out through the air communication port H510, as shown in FIG. 7D.
In order to prevent such an ink leakage, an ink un-permeated layer 310 of the ink absorption member H300 can be formed that is comparatively thicker, so that the loss of the layer H310 may be avoided, even when the freezing and melting of ink H400 is repeated several times. That is, it is preferable that a flat, thick, ink un-permeated layer H310 be obtained when ink H400 has been permeated the ink absorption member H300. More specifically, it is preferable that the ink filling process be performed so as to provide an ink un-permeated layer H310 having a uniform thickness in order to obtain a certain thickness of the ink un-permeated layer within a limited size of ink tank.
A conventional example of injecting ink into an ink absorber is disclosed in Japanese Patent Laid-Open No. 2006-159656, in which a plurality of ink injection needles are employed to inject ink into the ink absorption member. According to the filling method described in Japanese Patent Laid-Open No. 2006-159656, a volume of ink to be supplied to an ink absorption member is adjusted for each injection needle to obtain the uniform ink permeated state.
In a method described in Japanese Patent Laid-Open No. 2006-159656, which injects ink into an absorption member using a plurality of ink injection needles 300, balancing the volume of ink supplied by each of the multiple ink injection needles 300 is important. When a good balance is secured for the volumes of ink supplied by the respective ink injection needles 300, the uniform ink permeated state shown in FIG. 8A is attained. However, once the balance for the volumes of ink supplied by the respective ink injection needles 300 is lost, the volume of ink H400 permeating an ink absorption member H300 is changed, and as shown in FIG. 8B, the ink permeated state becomes non-uniform. As a result, the thickness of an ink un-permeated layer H310 is also non-uniform.
To prevent this problem, in the conventional method described in Japanese Patent Laid-Open No. 2006-159656, filling syringes are required for the respective ink injection needles to balance the volumes of ink supplied by the respective ink injection needles 300. However, in this case, an increased number of parts is required for an ink filling device, which thus becomes larger and more complicated.
Furthermore, there is a case wherein, for a compact ink tank, the space originally available is insufficient for employing a plurality of ink injection needles.
On the other hand, an ink supplying arrangement that employs a single ink injection needle 300, may attain a uniform ink permeated state, if ink filling amount per unit time is extremely made small. For example, when a filling period of about one minute is provided for an ink tank having an ink capacity of 24 g, a uniform ink permeated state can be attained. However, in this case, the tact time required by the ink filling device is dramatically extended, and thus, to provide increased production efficiency, additional injection devices are required. This then becomes but one of the reasons why this solution will not provide a production cost reduction.